With the recent increases in communication intelligence data, various communication systems have been rapidly evolving with the use of microwave and millimeter-wave regions such as automobile communications, satellite communications and satellite broadcastings and, in its turns, there have been developed various dielectric materials. From the standpoint of production cost, there have been developed dielectric materials in which metallic materials (for example, silver, copper and so on) having high electric conductivity and low cost are usable as conductors. These materials are used in electronic parts such as resonators and LC filters (see, for example, JP-A-5-319920, JP-A-5-319922 and JP-A-6-116023).